Fibers have been produced in the past by various methods from glass, slag, fusible rock, and various other materials. Commercial manufacture of fibers from molten glass has been accomplished by subjecting the softened material to high velocity gaseous blasts which attenuate the material to fibers. Steam, compressed air, and hot exhaust gases from a combustion burner have been used as attenuating forces in the known process. Other processes utilize centrifugal or rotary forces for delivering bodies of glass into an annularly shaped gaseous blast which attenuates the glass into fine fibers.
The glass composition to be used with such a process must have particular physical properties which make it possible to use the glass in the process. The rotary process referred to comprises delivering into a rotor or spinner operating at high speed the material which has been heat-softened. The material is then directed outwardly through openings in the periphery of the spinner as individual bodies which are delivered generally radially of the spinner into the annular blast from a burner. The glass compositions of this invention are melted by conventional practices known to the art and require no special treatment during melting or fining.